I was thinking it is about time to re-bed the stanchions. And was wondering why no one has ever mentioned using a rubber gasket under the base rather than caulking. I can't really come up with a reason it would not work. But I am sure you folks will tell me the folly of my idea

It will leak and allow too much movement. Stanchions need hard surfaces in actual contact to prevent movement, and the sealant is just to fill gaps. Hairline cracks and seams will allow water to leach.

Also -- some people allow sealant to set before tightening down the screws/bolts, then tighten some more. I don't agree with that approach because it breaks the sealant bond surrounding the screws/bolt heads and threads. The bond is important, so my approach is:

1) clean hardware and surfaces in solvent to eliminate oils and contaminants from the maker's machining of the hardware.
2) Apply sealant and tighten down hardware, but not too tight -- over-tightening fasteners in fiberglass can cause internal crushing and create weak points.
3) You're done.

I would guess that over time the gasket would compress and you would need to tighten the bolts. I used a neoprene gasket on the cockpit sole that removes for major engine work. Its been fine. But its a different use. What Ive taken to doing when bedding is not to tighten down on the fasteners all the way until the goop has cured for a day then crank down on the bolts. This works very well in most places.

My last boat had many fittings bedded with gaskets; mostly cheek blocks. It was very successful, and none leaked during the life of the block. Retightening was not needed.

This would only work for through-bolted fittings; screws will not provide consistent compression. This would only work if the deck was very flat in the area. I have also seen many failures in gasketed seals, where there was curvature or the fasteners could not provide enough force. More failures than successes, I think.

However, I agree that for a stanchion this would allow too much motion. I like butyl rubber for large through bolted fittings and hatches to decks, and several different polyurethanes for smaller stuff and screwed on stuff.

We've had crews crash against stanchions and found the best bet is to have a larger solid bearing surface between the stanchion and the deck with big backing plates. Polysulfide for the sealant.

Quote:

Originally Posted by JusDreaming

I was thinking it is about time to re-bed the stanchions. And was wondering why no one has ever mentioned using a rubber gasket under the base rather than caulking. I can't really come up with a reason it would not work. But I am sure you folks will tell me the folly of my idea